This invention relates generally to gas turbine engines, and more specifically to a gas turbine engine and method of assembling a gas turbine engine.
At least some known gas turbine engines include, in serial flow arrangement, a high-pressure compressor for compressing air flowing through the engine, a combustor in which fuel is mixed with the compressed air and ignited to form a high temperature gas stream, and a high pressure turbine. The high-pressure compressor, combustor and high-pressure turbine are sometimes collectively referred to as the core engine. Such gas turbine engines may also include a low-pressure turbine or power turbine for transmitting power generated by the core engine to a driven component, such as a generator, for example.
Gas turbine engines are used in many applications, including aircraft, power generation, and marine applications. At least some known gas turbine engines include two thrust mounts that are coupled between an exterior surface of the gas turbine engine and a support structure. During engine operation, at least some known thrust mounts may cause at least some structural distortion or “out of round” condition of the gas turbine engine casing which may reduce blade tip clearances within the gas turbine engine. Moreover, when a power turbine is coupled to the core gas turbine engine, the combination of loads and geometries may also cause some structural distortion which may also reduce blade tip clearances within the gas turbine engine.
For example, during operation, the thrust load generated by at least some known power turbine rotors is approximately 250,000 lb in a direction that is opposite to the direction of thrust generated by the gas turbine engine. Accordingly, during operation, thrust generated by the power turbine is transferred to the engine thrust mounts, thus increasing the possibility that the gas turbine engine may experience structural distortion, or an “out of round” condition. Alternatively, thrust generated by the power turbine may be transferred to the power turbine thrust bearing support which may also increase the possibility that the gas turbine engine may experience structural distortion. To facilitate reducing such structural distortion, at least some known turbines attempt to balance loading between the engine thrust mounts and the power turbine thrust bearing support. However, even if the power turbine thrust load is balanced between the engine thrust mounts and the power turbine thrust bearing support, the combined power turbine rotor load and the gas turbine engine residual load may cause the core gas turbine engine casing to distort which may reduce blade tip clearances within the gas turbine engine.